Baseband wireless network for isochronous communication

ABSTRACT

A wireless communication network system apparatus which provides for isochronous data transfer between node devices of the network, which provides at least one master node device which manages the data transmission between the other node devices of the network, which avoids or reduces interference from other wireless products and which resolves random errors associated with wireless technology including multipath fading. The system provides a communication protocol which shares the wireless transport medium between the node devices of the network, and which provides each node device on the network a designated transmit time slot for data communication.

This is a continuation of 09/393,126, filed Sep. 10, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains generally to network systems for exchanging dataacross a shared medium. More particularly, the invention is a wirelesscommunication network system for isochronous data transfer between nodedevices of the network system that provides at least one master nodedevice which manages the data transmission between slave node devices ofthe network system, and which further provides a time division multipleaccess frame definition which provides each node device on the networksystem a transmit time slot for communication.

2. The Prior Art

Network systems for data communication exchange have been evolving forthe past several decades. Particularly, computer network systems havebeen developed to exchange information and provide resource sharing.Network systems generally comprise one or more node devices which areinterconnected and capable of communicating. The most common networksystems today are “wired” local area networks (LANs) and wide areanetworks (WANs). Normally, node devices participating in such wirednetworks are physically connected to each other by a variety oftransmission medium cabling schemes including twisted pair, coaxialcable, fiber optics and telephone systems including time divisionswitches (T-1, T-3), integrated services digital network (ISDN), andasymmetric digital subscriber line (ADSL). While wired solutions provideadequate bandwidth or data throughput between node devices on thenetwork, users participating in such networks are generally restrictedfrom mobility. Typically, users participating in a wired network arephysically limited to a specific proximity by the length of the cableattached to the user's node device.

Many common network protocols in use today are asynchronous and packetbased. One of the most popular is Ethernet or IEEE 802.3. These types ofnetworks are optimized for bursts of packetized information with dynamicbandwidth requirements settled on-demand. This type of network workswell for many data intensive applications in computer networks but isnot ideal for situations requiring consistent delivery of time-criticaldata such as media streams.

Media streams typically require connection oriented real-time traffic.Most media stream applications need to establish a required level ofservice. Dedicated connections are required with a predictablethroughput. Low traffic jitter is often a necessity and can be providedwith the use of a common network clocking reference.

Firewire, or IEEE 1394, is an emerging wireline network technology thatis essentially asynchronous, but provides for isochronous transfers or“sub-actions”. Isochronous data is given priority, but consistent timeintervals of data transfer is limited by mixing isochronous and purelyasynchronous transfers.

Universal Serial Bus (USB) is a popular standard for computer peripheralconnections. USB supports isochronous data transfer between a computerand peripheral devices. The computer serves as bus master and keeps thecommon clock reference. All transfers on USB must either originate orterminate at the bus master, so direct transfers between two peripheraldevices is not supported.

Wireless transmission provides mobile users the ability to connect toother network devices without requiring a physical link or wire.Wireless transmission technology provides data communication through thepropagation of electromagnetic waves through free space. Variousfrequency segments of the electromagnetic spectrum are used for suchtransmission including the radio spectrum, the microwave spectrum, theinfrared spectrum and the visible light spectrum. Unlike wiredtransmission, which is guided and contained within the physical mediumof a cable or line, wireless transmission is unguided, and propagatesfreely though air. Thus the transport medium air in wirelesscommunication is always shared between various other wireless users. Aswireless products become more pervasive, the availability of airspacefor data communication becomes proportionally more limited.

Radio waves travel long distances and penetrate solid objects and arethus useful for indoor and outdoor communication. Because radio wavestravel long distances, radio interference between multiple devices is acommon problem, thus multiple access protocols are required among radiodevices communicating using a single channel. Another common problemassociated with wireless transmission is multi-path fading. Multipathfading is caused by divergence of signals in space. Some waves may berefracted off low-lying atmospheric layers or reflected off objects suchas buildings and mountains, or indoors off objects such as walls andfurniture and may take slightly longer to arrive than direct waves. Thedelayed waves may arrive out of phase with the direct waves and thusstrongly attenuate or cancel the signal. As a result of multipathfading, operators have resorted to keeping a percentage of theirchannels idle as spares when multipath fading wipes out some frequencyband temporarily.

Infrared communication is widely used for short-range communication. Theremote controls used on televisions, VCRs, and stereos all use infraredcommunication. The major disadvantage to infrared waves is that they donot pass through solid objects, thus limiting communication betweendevices to “line of sight”. These drawbacks associated with the currentimplementation of wireless technology in network systems have resultedin mediocre performance and periodic disruption of operations.

In addition to the above noted drawbacks of Firewire and USB, there arecurrently no standards for wireless implementations of either. Of thewireless networks in use today, many are based at least in part on theIEEE 802.11 (wireless ethernet) extension to IEEE 802.3. Like wirelessethernet, this system is random access, using a carrier sense multipleaccess with collision detect (CSMA-CD) scheme for allowing multipletransmitters to use the same channel. This implementation suffers fromthe same drawback of wireline ethernet described above.

A similar implementation intended for industrial use is that ofHyperlan™. While still an asynchronous protocol, Hyperlan™ uses priorityinformation to give streaming media packets higher access to the randomaccess channel. This implementation reduces, but does not eliminate theproblems of sending streaming media across asynchronous networks.

The Home-RF consortium is currently working on a proposal for a wirelessnetwork specification suitable for home networks. The current proposalspecifies three types of wireless nodes, the connection points (CP),isochronous devices (I-nodes), and asynchronous devices (A-nodes).Isochronous transfers on the Home-RF network are intended for 64-kbpsvoice (PSTN) services and are only allowed between I-node devices andthe CP device that is connected to the PSTN network. There is noallowance in the Home-RF specification for alternative methods ofisochronous communication such as might be required for high qualityaudio or video.

The Bluetooth Special Interest Group™ has developed a standard for ashort range low bit-rate wireless network. This network standard doesovercome some of the shortcomings of random access networks, but stilllacks some of the flexibility needed for broadband media distribution.The Bluetooth network uses a master device which keeps a common clockfor the network. Each of the slave devices synchronizes their localclock to that of the master, keeping the local clock within +/−10microseconds (μsecs). Data transfer is performed in a Time DivisionMultiple Access (TDMA) format controlled by the master device. Two typesof data links are supported: Synchronous Connection Oriented (SCO) andAsynchronous Connection-Less (ACL). The Master can establish a symmetricSCO link with a slave by assigning slots to that link repeating withsome period Tsco. ACL links between the master and slave devices aremade available by the Master addressing slave devices in turn andallowing them to respond in the next immediate slot or slots. Broadcastmessages are also allowed originating only at the master with no directresponse allowed from the slave devices.

Several limitations exist in the Bluetooth scheme. All communicationlinks are established between the master device and the slave devices.There are no allowances for slave-slave communication using eitherpoint-to-point or broadcast mechanisms. Additionally, isochronouscommunications are only allowed using symmetric point-to-point linksbetween the master device and one slave device. The TDMA structure usedby Bluetooth is also limiting in that slot lengths are set at N*625μsecs where N is an integer 0<=1<=5.

All of the above wireless network schemes use some form of continuouswave (CW) communications, typically frequency hopping spread spectrum.The drawbacks of these systems are that they suffer from multipathfading and use expensive components such as high-Q filters, preciselocal high-frequency oscillators, and power amplifiers.

Win et. al. have proposed using time-hopping spread spectrum multipleaccess (TH-SSMA), a version of Ultra-Wide Band (UWB), for wirelessextension of Asynchronous Transfer Mode (ATM) networks which isdescribed in the article to Win, Moe Z., et. al. entitled “ATM-BasedTH-SSMA Network for Multimedia PCS” published in “IEEE Journal onselected areas in communications”, Vol. 17, No. May 5, 1999. Theirsuggestion is to use TH-SSMA as a wireless “last hop” between a wirelineATM network and mobile devices. Each mobile device would have a uniqueconnection to the closest base station. Each mobile-to-base connectionwould be supplied with a unique time hopping sequence. Transfers wouldhappen asynchronously with each node communicating with the base at anytime using a unique hopping sequence without coordinating with othermobile devices.

There are significant drawbacks to the TH-SSMA system for supportingmedia stream transfers between devices of the network. This method isdesigned to link an external switched wireline network to mobile nodes,not as a method of implementing a network of interconnected wirelessnodes. This method relies on the external ATM network to control thevirtual path and virtual connections between devices. Base stations mustbe able to handle multiple simultaneous connections with mobile devices,each with a different time hopping sequence, adding enormously to thecost and complexity of the base station. Transfers between mobiledevices must travel through the base station using store and forward.Finally, all mobile nodes are asynchronous, making truly isochronoustransfers impossible.

Accordingly, there is a need for a wireless communication network systemapparatus which provides for isochronous data transfer between nodedevices of the network, which provides at least one master node devicewhich manages the data transmission between the other node devices ofthe network, and which provides a means for reducing random errorsinduced by multipath fading, and which further provides communicationprotocol to provide a means for sharing the transport medium between thenode devices of the network so that each node device has a designatedtransmit time slot for communicating data. The present inventionsatisfies these needs, as well as others, and generally overcomes thedeficiencies found in the background art.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is a wireless communication network system forisochronous data transfer between node devices. In general, the networksystem comprises a plurality of node devices, wherein each node deviceis a transceiver. Each transceiver includes a transmitter or other meansfor transmitting data to the other transceivers as is known in the art.Each transceiver also includes a receiver or other means for receivingdata from the other transceivers as is known in the art. One of thetransceivers is preferably structured and configured as a “master”device. Transceivers other than the master device are structured andconfigured as “slave” devices. The master device carries out theoperation of managing the data transmission between the node devices ofthe network system. The invention further provides means for framingdata transmission and means for synchronizing the network.

By way of example, and not of limitation, the data transmission framingmeans comprises a Medium Access Control protocol which is executed oncircuitry or other appropriate hardware as is known in the art withineach device on the network. The Medium Access Control protocol providesa Time Division Multiple Access (TDMA) frame definition and a framingcontrol function. The TDMA architecture divides data transmission timeinto discrete data “frames”. Frames are further subdivided into “slots”.The framing control function carries out the operation of generating andmaintaining the time frame information by delineating each new frame byStart-Of-Frame (SOF) symbols. These SOF symbols are used by each of theslave devices on the network to ascertain the beginning of each framefrom the incoming data stream.

In the preferred embodiment, the frame definition comprises a masterslot, a command slot, and a plurality of data slots. The master slot isused for controlling the frame by delineating the SOF symbols. Asdescribed in further detail below, the master slot is also used forsynchronizing the network. The command slot is used for sending,requesting and authorizing commands between the master device and theslave devices of the network. The master device uses the command slotfor ascertaining which slave devices are online, offline, or engaged indata transfer. The master device further uses the command slot forauthorizing data transmission requests from each of the slave devices.The slave devices use the command slot for requesting data transmissionand indicating its startup (online) or shutdown (offline) state. Thedata slots are used for data transmission between the node devices ofthe network. Generally, each transmitting device of the network isassigned one or more corresponding data slots within the frame in whichthe device may transmit data directly to another slave device withoutthe need for a “store and forward” scheme as is presently used in theprior art. Preferably, the master dynamically assigns one or more dataslots to slave devices which are requesting to transmit data.Preferably, the data slots are structured and configured to havevariable bit lengths having a granularity of one bit. The presentinvention provides that the master device need not maintaincommunication hardware to provide simultaneous open links between itselfand all the slave devices.

Broadcast is supported with synchronization assured. This guaranteesthat media can be broadcast to many nodes at the same time. This methodallows, for example, synchronized audio data to be sent to severalspeakers at the same time, and allows left and right data to be sent inthe same frame.

Asynchronous communication is allowed in certain slots of the framethrough the use of either master polling or CSMA-CD after invitationfrom the master.

The means for synchronizing the network is preferably provided by aclock master function in the master device and a clock recovery functionin the slave devices. Each node device in the network system maintains aclock running at a multiple of the bit rate of transmission. The clockmaster function in the master device maintains a “master clock” for thenetwork. At least once per frame, the clock master function issues a“master sync code” that is typically a unique bit pattern whichidentifies the sender as the clock master. The clock recovery functionin the slave devices on the network carries out the operation ofrecovering clock information from the incoming data stream andsynchronizing the slave device to the master device using one or morecorrelators which identifies the master sync code and a phase or delayedlocked loop mechanism. In operation, the clock master issues a “mastersync code” once per frame in the “master slot”. A slave device trying tosynchronize with the master clock will scan the incoming data stream fora master sync code using one or more correlators. As each master synccode is received, the phase or delayed locked loop mechanism is used toadjust the phase of the slave clock to that of the incoming data stream.By providing a common network clock on the master device, with slavedevices synchronizing their local clocks to that of the master clock,support for synchronous and isochronous communication in additional toasynchronous communication is provided. Time reference between alldevice nodes is highly accurate eliminating most latency and timingdifficulties in isochronous communication links.

As noted above, each transceiver carries out the operation oftransmitting and receiving data. In wireless transmission, data istransmitted via electromagnetic waves, which are propagated through freespace. In the preferred embodiment, the invention provides datatransmission via baseband wireless technology. This method uses shortRadio Frequency (RF) pulses to spread the power across a large frequencyband and as a consequence reduces the spectral power density and theinterference with any device that uses conventional narrowbandcommunication. This method of transmitting short pulses is also referredto as Ultra Wide Band technology. This present implementation providesbaseband wireless transmission without any carrier. Use of basebandwireless greatly reduces multipath fading and provides a cheaper, easierto integrate solution by eliminating a sinewave carrier. According tothe invention, there is no carrier to add, no carrier to remove, andsignal processing may be done in baseband frequencies.

Additionally, using short pulses provides another advantage overContinuous Wave (CW) technology in that multipath fading can be avoidedor significantly reduced.

The present invention further provides a modulator or other means formodulating data as is known in the art, a demodulator or other means fordemodulating data as is known in the art, and a gain controller or othermeans for controlling the gain of each of the transceivers. In thepreferred embodiment, the means for modulating data comprises amodulator which converts the TDMA frames into streams of basebandpulses. The means for demodulating data comprises a demodulator whichconverts incoming baseband pulses into TDMA frames.

In a first embodiment, the invention provides pulse modulation anddemodulation with on/off keying. The transmitting device modulates a “1”into a pulse. A “0” is indicated as the absence or lack of a pulse. Thereceiver locks on to the transmitted signal to determine where to samplein the incoming pulse streams. If a pulse appears where the signal issampled, a “1” is detected. If no pulse appears, a “0” is detected.

In another exemplary embodiment, the invention provides pulse modulationand demodulation using a pulse amplitude modulation scheme. Here, thetransmitting device modulates a digital symbol as a pulse amplitude. Forexample, a three bit symbol can be represented with eight levels ofpulse amplitude. The receiver locks on to the transmitted signal todetermine where to sample the incoming pulse stream. The level of thepulse stream is sampled, and the pulse amplitude is converted to adigital symbol.

The gain controlling means carries out the operation of adjusting theoutput gain of the transmitter and adjusting the input gain of thereceiver.

The network system also includes a hardware interface within the DataLink Layer of the Open Systems Interconnection (OSI) Reference Modelcomprising a multiplexer/demultiplexer unit and a plurality of slotallocation units.

The master devices described herein, in addition to carrying out itsfunctions as a master device, may also carry out functions as a slavedevice as described above. For example, the master device may alsoengage in data transfer of non-protocol related data with a slavedevice.

An object of the invention is to provide a baseband wireless networksystem which overcomes the deficiencies in the prior art.

Another object of the invention is to provide a baseband wirelessnetwork system which provides isochronous data communication between atleast two node devices on the network.

Another object of the invention is to provide a baseband wirelessnetwork system which provides a master device which manages network datacommunication between the other nodes devices of the network.

Another object of the invention is to provide a baseband wirelessnetwork system which provides a time division multiple access framedefinition which provides each node device on the network at least onetransmit time slot for data communication.

Another object of the invention is to provide a baseband wirelessnetwork system which provides a time division multiple access framedefinition which provides means for sharing the data communicationmedium between the node devices on the network.

Another object of the invention is to provide a baseband wirelessnetwork system which provides baseband wireless data communicationbetween the node devices of the network.

Further objects and advantages of the invention will be brought out inthe following portions of the specification, wherein the detaileddescription is for the purpose of fully disclosing the preferredembodiment of the invention without placing limitations thereon.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The present invention will be more fully understood by reference to thefollowing drawings, which are for illustrative purposes only.

FIG. 1 is a functional block diagram showing a network system inaccordance with the invention.

FIG. 2 is a functional block diagram of a transceiver node device inaccordance with the invention.

FIG. 3 a is a functional block diagram of a master clock synchronizationunit.

FIG. 3 b is a functional block diagram of a slave clock synchronizationunit.

FIG. 4 is a time division multiple access frame definition in accordancewith the present invention.

FIG. 5 is a functional block diagram of the Medium Access Controlhardware interface of the present invention.

FIG. 6 is a functional block diagram of a slot allocation unit providedin the Medium Access Control hardware.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Persons of ordinary skill in the art will realize that the followingdescription of the present invention is illustrative only and not in anyway limiting. Other embodiments of the invention will readily suggestthemselves to such skilled persons having the benefit of thisdisclosure.

Referring more specifically to the drawings, for illustrative purposesthe present invention is embodied in the apparatus shown FIG. 1 throughFIG. 6. It will be appreciated that the apparatus may vary as toconfiguration and as to details of the parts, and that the method mayvary as to details and the order of the steps, without departing fromthe basic concepts as disclosed herein. The invention is disclosedgenerally in terms of a wireless network for isochronous datacommunication, although numerous other uses for the invention willsuggest themselves to persons of ordinary skill in the art.

Referring first to FIG. 1, there is shown generally a wireless networksystem 10 in accordance with the invention. The network system 10comprises a “master” transceiver device 12 and one or more “slave”transceiver devices 14 a through 14 n. The master device may also bereferred to as a “base” transceiver, and slave devices may also bereferred to as “mobile” transceivers. Master transceiver 12 and slavetransceivers 14 a through 14 n include a transmitter or other means fortransmitting data to the other transceivers of the network 10 via acorresponding antenna 18, 20 a through 20 n. Transceivers 12, 14 athrough 14 n further include a receiver or other means for receivingdata from the other transceivers via its corresponding antenna 18, 20 athrough 20 n. While the illustrative network 10 shows the transceiverdevices 12, 14 a through 14 n using a corresponding single sharedantenna 18, 20 a through 20 n for both transmission and reception,various arrangements known in the art may be used for providing thefunctions carried out by the antenna 18, 20 a through 20 n, includingfor example, providing each of the transceiver devices 12, 14 a through14 n a first antenna for transmission and a second antenna forreception.

As described further below, the master transceiver 12 carries out theoperation of managing network communication between all transceivers 12,14 a through 14 n of the network 10. The master transceiver 12 includesmeans for managing the data transmission between the transceiver nodesof the network 10 as described further below.

Referring now to FIG. 2 as well as FIG. 1, a functional block diagram ofthe “Physical layer” implementation of a transceiver node device 22 inaccordance with the present invention is shown. The “Physical layer” asdescribed herein refers to the Physical layer according to the OpenSystems Interconnection (OSI) Reference Model. This model is based on aproposal developed by the International Standards Organization (ISO) todeal with connecting systems that are open for communication with othersystems.

Master transceiver 12 and slave transceivers 14 a through 14 n of thenetwork 10 are structured and configured as transceiver device 22 asdescribed herein. The transceiver node device 22 comprises an integratedcircuit or like hardware device providing the functions described below.Transceiver device 22 comprises an antenna 24, a transmitter 26connected to the antenna 24, a data modulation unit 28 connected to thetransmitter 26, and an interface to Data Link Layer (DLL) 30 connectedto the data modulation unit 28. The transceiver device 22 also includesa receiver 32 connected to the antenna 24 and a data demodulation unit34 connected to the receiver 32 and to the interface to the interface toData Link Layer (DLL) 30. A receive gain control unit 36 a is connectedto the receiver 32, a transmit gain control unit 36 b is connected tothe transmitter 26. A framing control unit 38 is operatively coupled tothe data modulation unit 28 and the data de-modulation unit 34. A clocksynchronization unit 40 is also operatively coupled to the datamodulation unit 28 and the data demodulation unit 34.

Antenna 24 comprises a radio-frequency (RF) transducer as is known inthe art and is preferably structured and configured as a receivingantenna and/or a transmitting antenna. As a receiving antenna, antenna24 converts an electromagnetic (EM) field to an electric current, and asa transmitting antenna, converts an electric current to an EM field. Inthe preferred embodiment, antenna 24 is structured and configured as aground plane antenna having an edge with a notch or cutout portionoperating at a broad spectrum frequency ranging from about 2.5 gigahertz(GHz) to about 5 GHz with the center frequency at about 3.75 GHz. Itwill be appreciated that antenna 24 may be provided with variousgeometric structures in order to accommodate various frequency spectrumranges.

Transceiver node device 22 includes hardware or circuitry which providesan interface to data link layer 30. The interface to data link layer 30provides an interface or communication exchange layer between thePhysical layer 22 and the “higher” layers according to the OSI referencemodel. The layer immediately “above” the Physical layer is the data linklayer. Output information which is transmitted from the data link layerto the interface 30 is communicated to the data modulation unit 28 forfurther data processing. Conversely, input data from thedata-demodulation unit 34 is communicated to the interface 30, whichthen transfers the data to the data link layer.

Transceiver node device 22 includes hardware or circuitry providing datamodulation functions shown generally as data modulation unit 28. Thedata modulation unit 28 carries out the operation of converting datareceived from the interface 30 into an output stream of pulses. In thecase of pulse amplitude modulation, the amplitude of the pulserepresents a value for that symbol. The number of bits represented by apulse depends on the dynamic range and the signal to noise ratio. Thesimplest case comprises on-off keying, where the presence of a pulse ofany amplitude represents a “1”, and the absence of a pulse represents“0”. In this case, data modulation unit 28 causes a pulse to betransmitted at the appropriate bit time to represent a “1” or no pulseto be transmitted at the appropriate time to represents a “0”. Asdescribed further below, the pulse stream produced by transceiver 22must be synchronous with a master clock of the network 10 and must besent at the appropriate time slot according to a frame definitiondefined for the network. The pulse stream is then communicated totransmitter 26 for transmission via antenna 24.

Transceiver node device 22 includes hardware or circuitry providingmeans for transmitting data to other transceivers on the network showngenerally as transmitter 26. The transmitting means of transceiver 22preferably comprises a wide band transmitter 26. Transmitter 26 isoperatively coupled to the data modulation unit 28 and to the antenna24. Transmitter 26 carries out the operation of transmitting the pulsestream received from modulation unit 28 and transmitting the pulsestream as electromagnetic pulses via antenna 24. In the preferredembodiment, information is transmitted via impulses having 100picosecond (ps) risetime and 200 ps width, which corresponds to the 2.5through 5 GHz bandwidth.

Transceiver node device 22 includes hardware or circuitry which providesmeans for receiving data from other transceivers shown generally asreceiver 32. The receiving means of transmitter 22 preferably comprisesa wide band receiver 32. Receiver 32 is operatively coupled to theantenna 24 and the data demodulation unit 34. Receiver 32 carries outthe operation of detecting electromagnetic pulse signals from antenna 24and communicating the pulse stream to the data de-modulation unit 34.The received signal does not necessarily have the same spectrum contentas the transmitted signal, and the spectrum content for received andtransmitted signals vary according to the receive and transmit antennaimpulse response. Typically, the received signal is shifted toward alower frequency than the transmitted signal.

Transceiver node device 22 further includes hardware or circuitryproviding means for controlling the gain of signals received andtransmitted shown generally as gain control units 36 a, 36 b. Thetransmit gain control unit 36 b carries out the operation of controllingthe power output of the transmitter 26 and receive gain control unit 36a carries out the operation of controlling the input gain of thereceiver 32.

As indicated above, the pulse stream produced by modulator 28 must besynchronous with the master clock of the network 10. In order tomaintain a synchronized network, one device must serve the function ofbeing a clock master and maintain the master clock for the network.Preferably, the master device 12 carries out the operation of the clockmaster. All other slave devices must synchronize with the master clock.The invention includes means for synchronizing the network system 10provided by the clock synchronization unit 40 in transceiver 22.

Referring to FIG. 3 a as well as FIG. 1 and FIG. 2, a functional blockdiagram of a clock synchronization unit 40 a for the master device 12 isshown. In the master device 12, the clock synchronization unit 40 aincludes hardware or circuitry providing the functions described herein.Clock synchronization unit 40 a comprises a clock master function 42which maintains a master clock 44 for the network 10. The master clock44 runs at a multiple of the bit rate. As described in further detailbelow, transmit time is divided into “frames”, and transceiver devicesare assigned specific “slots” within each frame where the devices arepermitted to transmit data. At least once per frame, the clock masterfunction 42 issues a master sync code. The master sync code is a uniquebit pattern that does not appear anywhere else in the frame whichidentifies the sender as the master device 12.

Referring to FIG. 3 b as well as FIG. 1 and FIG. 2, a functional blockdiagram of a clock synchronization unit 40 b for the slave devices 14 athrough 14 n is shown. In the slave devices 14 a through 14 n, the clocksynchronization unit 40 b includes hardware or circuitry providing thefunctions described herein. Clock synchronization unit 40 b comprises alocal or slave clock 46 and a clock recovery function 48. The slaveclock 46 also runs at a multiple of the bit rate.

The clock recovery function 48 carries out the operation of scanning theincoming data stream received by receiver 32 to detect or otherwiseascertain the master sync code using one or more correlators. When theclock recovery function 48 detects the master sync code, the clockrecovery function 48 will predict when the next master sync code will betransmitted. If the new master sync code is detected where predicted,the transceiver 22 will be considered “locked” or otherwise synchronizedwith the clock master 42 and will continue to monitor and verify futureincoming master sync codes. If the clock recovery function 48 fails todetect a threshold number of consecutive master sync codes, lock will beconsidered lost. As each master sync code is received by thetransceiver, a phase or delayed locked loop mechanism is used to adjustthe phase of the slave clock 46 to that of the incoming pulse stream.

The clock recovery function 48 includes a master sync code correlator50. A slave transceiver trying to achieve synchronization or “lock” withthe master clock examines the incoming data stream to detect the mastersync code, as described above. The master sync code correlator 50carries out the operation of detecting the first incoming pulse andattempting to match each of the next arriving pulses to the nextpredicted or pre-computed pulse. After the initial master sync code isdetected, the clock recovery function 48 of the slave transceiver devicewill perform a coarse phase adjustment of its bit-clock to be close tothat of the incoming pulse stream. When the next master sync code isexpected, a mask signal is used to examine the incoming pulse trainstream only where valid pulses of the incoming master sync code areexpected. The primary edge of the incoming pulse is compared with therising edge of the local clock, and any difference in phase is adjustedusing a phase-locked loop mechanism. If the incoming pulse streammatches the master sync code searched for, the correlator 50 signals asuccessful match. If the incoming pulse stream differs from the mastersync code, the process is repeated. Multiple correlators may be used toperform staggered parallel searches in order to speed up the detectionof the master sync code.

The clock recovery function 48 further includes a phase lock mechanism52. As each predicted master sync code is detected at the slavetransceivers, the phase lock mechanism 52 carries out the operation ofdetermining the phase difference between the local slave clock 46 andthe incoming pulses. The phase lock mechanism 52 adjusts the phase ofthe slave clock 46 so that the frequency and phase of the slave clock 46is the same as that of the incoming pulses, thereby locking orsynchronizing the local slave clock 46 to master clock 44 of the mastertransceiver 12.

Referring again to FIG. 2, as well as FIG. 1, the transceiver nodedevice 22 includes hardware or circuitry which provides demodulatingfunctions and is shown generally as data demodulation unit 34. The datademodulation unit 34 carries out the operation of converting the inputpulse stream from receiver 32 into a data stream for higher protocollayers. The data de-modulation unit 34 comprises a phase offset detector54 and a data recovery unit 56. In an isochronous baseband wirelessnetwork, data streams will be received from different transceivers withdifferent phase offsets. The phase offset is due to path propagationdelays between the transmitter, the receiver and the master clock 44.

As described in further detail below, a transmitter will be assigned adata “slot” within a frame to transmit to another device. The phaseoffset detector 54 carries out the operation of ascertaining the phasedelay between the expected zero-delay pulse location, and the actualposition of the incoming pulses. Typically, a known training bit patternis transmitted before the data is transmitted. The phase offset detector54 in the receiving device detects or otherwise ascertains the trainingbit pattern and determines the phase offset of the incoming pulse fromthe internal clock. The phase determined is then communicated to theData Recovery Unit 56. In the case of pulse amplitude modulation, thetraining sequence is also used to provide a known pulse amplitudesequence against which the modulated pulse amplitudes can be compared inthe data transmission.

The Data Recovery Unit 56 in a receiving device carries out theoperation of converting the incoming pulse stream data into bit dataduring time slots that a transmitting device is sending data to thereceiving device. In the case of on-off keying modulation, the datarecovery unit 56 carries out the operation of examining the pulse streamduring the designated time slot or “window” for the presence or absenceof a pulse. In pulse amplitude modulation, the data recovery unit 56carries out the operation of examining the pulse stream during thedesignated time slot or “window” to ascertain the amplitude of the pulsesignal. The “window” or time slot in which the receiving device examinespulse stream data determined by the expected location of the bit due tothe encoding mechanism and the offset determined by the phase offsetdetector 54. The information converted by the data de-modulation unit 34is then communicated to the interface to data link layer 30 for furtherprocessing.

Referring now to FIG. 4 as well as FIG. 1 and FIG. 2, a Time DivisionMultiple Access (TDMA) frame definition is shown and generallydesignated as 58. The TDMA frame definition 58 is provided and definedby the data link protocol software of the present invention. Moreparticularly, the TDMA frame 58 is defined by the Medium Access Control(MAC) sublayer software residing within the Data Link Layer accordingthe OSI Reference model.

The means for managing the data transmission between the transceivernodes of the network 10 is provided by software algorithms running andexecuting in the Medium Access Control. The Medium Access Controlprotocol provides algorithms, routines and other program means formanaging and controlling access to the TDMA frame definition 58 and itsassociated slot components. The architecture of TDMA frame definition 58provides for isochronous data communication between the transceivers 12,14 a through 14 n of the network 10 by providing a means for sharing thedata transmit time that permits each transceiver of the network totransmit data during a specific time chunk or slot. The TDMA framearchitecture divides data transmission time into discrete data “frames”.Frames are further subdivided into “slots”.

In the preferred embodiment, the TDMA frame definition 58 comprises amaster slot 60, a command slot 62, and a plurality of data slots 64 athrough 64 n. The master slot 60 contains a synchronizing beacon or“master sync”. More preferably, the “master sync” is the same code asthe “master sync code” as described earlier for clock synchronizationunit 40. The command slot 62 contains protocol messages exchangedbetween the transceiver devices of the network. Generally, each of thedata slots 64 a through 64 n provides data transmission time for acorresponding slave device 14 a through 14 n of the network 10.Preferably, each data slot assigned is structured and configured to havea variable bit width and is dynamically assigned by the master device.In an alternative arrangement, the slave devices 14 a through 14 nrequest the use of one or more of the data slots 64 a through 64 n fordata transmission. In either arrangement, the master may also beassigned one or more slots to transmit data to slave devices. If randomaccess devices are connected to the network, these devices may beassigned a common random access time slot by the master. These deviceswill communicate using a CSMA-CD or similar protocol within theallocated time slot.

As noted above, the transceiver device 22 includes a framing controlfunction 38. The framing control function 38 carries out the operationof generating and maintaining the time frame information. In the masterdevice 12 the framing control function 38 delineates each new frame byStart-Of-Frame (SOF) symbols. The SOF symbols are unique symbols, whichdo not appear anywhere else within the frame and mark the start of eachframe. In the preferred embodiment, the SOF symbols serve as the “mastersync” and as the “master sync code” for the network and are transmittedin the master slot 60 of frame 58. These SOF symbols are used by theframing control function 38 in each of the slave devices 14 a through 14n on the network to ascertain the beginning of each frame 58 from theincoming data stream. For example, in one illustrative embodiment, theinvention utilizes a 10-bit SOF “master sync” code of “0111111110”.

Various encoding schemes known in the art may be used to guarantee thatthe SOF code will not appear anywhere else in the data sequence of theframe. For example, a common encoding scheme is 4B/5B encoding, where a4-bit values is encoded as a 5-bit value. Several criteria or “rules”specified in a 4B/5B code table, such as “each encoded 5-bit value maycontain no more than three ones or three zeros” and “each encoded 5-bitvalue may not end with three ones or three zeros”, ensure that a pulsestream will not have a string of six or more ones or zeros. Othertechniques known in the art may also be used including, for example, bitstuffing or zero stuffing.

The master transceiver 12 carries out the operation of managing networkdata communication via the exchange of “protocol messages” in thecommand slot 62 of frame 58. The master transceiver 12 carries out theoperation of authenticating slave transceivers 14 a through 14 n,assigning and withdrawing data time slots 64 a through 64 n for theslave transceivers 14 a through 14 n, and controlling power of the slavetransceivers 14 a through 14 n.

Master transceiver 12 authenticates or registers each slave transceiverby ascertaining the “state” of each of the slave transceivers of thenetwork 10. Each transceiver operates as a finite-state machine havingat least three states: offline, online, and engaged. When a transceiveris in the offline state, the transceiver is considered “unregistered”and is not available for communication with the other devices on thenetwork 10. Each slave transceiver must first be “registered” withmaster transceiver 12 before the slave transceiver is assigned orallocated a data slot within the TDMA frame 58. Once a transceiver isregistered with the master transceiver 12, the device is considered“online”.

A slave transceiver that is in the “online” state is ready to send dataor ready to receive data from the other devices on the network 10.Additionally, an “online” transceiver is one which is not currentlytransmitting or receiving “non-protocol” data. Non-protocol data is dataother than that used for authenticating the “state” of the transceiverdevices.

A transceiver is “engaged” when the transceiver is currentlytransmitting and/or receiving “non-protocol” data. Each slave devicemaintains and tracks its state by storing its state informationinternally, usually in random access memory (RAM). The state of eachslave device is further maintained and tracked by the master device 12by storing the states of the slaves in a master table (not shown) storedin RAM.

In operation, the master transceiver 12 periodically broadcasts an ALOHApacket in the command slot 62 to ascertain or otherwise detect“unregistered” slave devices and to receive command requests from theslave transceivers of then network. More generally, an ALOHA broadcastis an invitation to slave transceivers to send their pending protocolmessages. This arrangement is known as “slotted ALOHA” because allprotocol messages including the ALOHA broadcast are sent during apredetermined time slot. In the preferred embodiment, the ALOHAbroadcast is transmitted at a predetermined interval. Responsive to thisALOHA packet and in the next immediate TDMA frame, an “unregistered”slave device 14 n transmits a signal in command slot 62 identifyingitself as slave device 14 n and acknowledging the master device with aregistration or “discovery” (DISC) request indicating additionalinformation, such as the bandwidth capabilities of the device. When theregistration request is received by the master transceiver 12, themaster table records in the master table that device 14 n is “online”.The master transceiver 12 also transmits a confirmation in command slot62 to the slave device 14 n that the state of slave device 14 n haschanged to “online”.

When the slave device 14 n receives the confirmation command from themaster device 12, the slave device 14 n then changes its internal stateto “online”. If more than one slave transceiver replies with anacknowledgement to an ALOHA broadcast in the same frame, a packetcollision may occur because both transceivers are attempting to occupythe same command slot 62 within the frame 58. When a collision isdetected in response to an ALOHA broadcast, the master transceiver 12transmits another ALOHA message directed to a subset of the slavedevices based on a binary-search style scheme, a random delay scheme orother similar searching means known in the art.

The master transceiver 12 also periodically verifies each slavetransceiver device that is “online” or “engaged” according the mastertable to ascertain whether any failures have occurred at the slavedevice using a “time-out” based scheme. According to this time-outscheme, the master transceiver 12 periodically transmits a POLL packetin command slot 62 to a specific “online” slave device 14 n from themaster table to ascertain the state of the slave device 14 n. In thepreferred embodiment, the master transceiver 12 transmits a POLL signalevery ten seconds. Responsive this POLL packet, slave device 14 ntransmits an acknowledgement signal in the command slot 62 of the nextimmediate frame identifying itself as slave device 14 n andacknowledging its state. Responsive to this acknowledgement signal, themaster transceiver 12 confirms verification of device 14 n and continueswith other tasks. In the event slave device 14 n is shutdown orotherwise unavailable, master transceiver 12 will not receive a returnacknowledgement and master transceiver 12 will fail to verify device 14n. After a predetermined number failed verifications from a slavedevice, a time-out is triggered, and the master transceiver 12 willchange the state of such slave device to “offline”.

In the command slot 62, the flow of protocol messages between thetransceivers is preferably governed by a “sequence retransmissionrequest” (SRQ) protocol scheme. The SRQ protocol framework providesconfirmation of a protocol transaction after the entire protocolsequence is completed. Effectiveness and success of the transmission ofa protocol sequence are acknowledged at the completion of the entireprotocol sequence rather than immediately after the transmission of eachmessage as in the traditional Automatic Retransmission reQuest (ARQ)approach. Because a protocol sequence may include a plurality ofprotocol messages, the overhead associated with acknowledging eachprotocol message is avoided, and bandwidth use is improved thereby. TheSRQ protocol scheme is described further detail in copending patentapplication entitled “MEDIUM ACCESS CONTROL PROTOCOL FOR CENTRALIZEDWIRELESS NETWORK COMMUNICATION MANAGEMENT” having attorney docket number“INT-99-005” filed on Sep. 10, 1999 which is expressly incorporatedherein by reference.

Referring again to FIG. 3 as well as FIG. 1 and FIG. 2, a plurality ofdata slots 64 a through 64 n is provided for each slave transceiver 14 athrough 14 n of the network 10 which is registered as “online”. Themaster transceiver 12 further manages the transmission of information inslots 64 a through 64 n through traditional Time Division MultipleAccess (TDMA). The command slot 62 operates in traditional TDMA mode inaddition to the “slotted ALOHA” mode described above for invitingprotocol messages from the slave transceivers as determined by themaster transceiver 12. The slotted ALOHA mode, which is active when themaster invites a protocol message, continues until the slave protocolmessage is received without collision. Once the slave protocol messagesis received or “captured” by the master transceiver, the command slotoperates in a regular TDMA mode until the entire protocol exchangesequence between the master device and the “captured” slave device iscompleted. Traditional TDMA mode is used, for example, when a firstslave transceiver makes a data link request to the master transceiver inorder to communicate data to a second slave transceiver.

For example, a first slave transceiver 14 a (microphone) has audio datato transmit to a second slave transceiver 14 b (speaker). The mastertransceiver 12 manages this data transaction in the manner and sequencedescribed herein. As indicated above, the master transceiverperiodically sends an ALOHA broadcast to invite protocol messages fromthe slave devices of the network. Responsive to this ALOHA broadcast,slave transceiver 14 a transmits a data-link request (REQ) to mastertransceiver 12 identifying itself as the originating transceiver andidentifying the target slave transceiver 14 b. Responsive to this REQrequest, the master transceiver 12 verifies the states of originating orsource transceiver 14 a and target transceiver 14 a according to themaster table. If both originating transceiver and target transceiver are“online” according to the master table, the master transceiver transmitsa base acknowledge (BACK) to the originating transceiver 14 a and aservice request (SREQ) to the target transceiver indicating the identityof the originating transceiver 14 a and assigns a data slot to theoriginating transceiver 14 a within the TDMA frame 58 for datacommunication. If target transceiver is “offline”, the mastertransceiver 12 transmits a base negative acknowledge (BNACK) packet tothe originating transceiver to confirm the unavailability of the targettransceiver. If the target transceiver is “engaged” in communicationwith another device, the master transceiver 12 transmits a base busy(BBUSY) packet to the originating transceiver to indicate theunavailability of the target transceiver.

When the originating transceiver 14 a receives the BACK packet, thetransceiver 14 a waits for a data-link confirmation from the mastertransceiver 1, after which the transceiver 14 a begins transmitting datawithin a dynamically assigned data slot. Responsive to the SREQ packetfrom the master transceiver 12, the target transceiver 14 b transmits areturn acknowledge (ACK) to the master transceiver 12 indicating thattransceiver 14 b is ready to receive data. The transceiver 14 b alsobegins to monitor the corresponding data slot assigned to theoriginating transceiver 14 a. Responsive to the return ACK from targettransceiver 14 b, the master transceiver 12 transmits a data-linkconfirmation to originating transceiver 14 a to indicate that targettransceiver is ready to receive data communication.

After originating transceiver 14 a completes its data transmission tothe target transceiver 14 b, the transceiver 14 a terminates its datalink by initiating a termination sequence. As indicated above, themaster transceiver 12 will periodically transmit an ALOHA broadcast tofind unregistered device nodes or to invite protocol requests fromregistered device nodes.

The termination sequence comprises communicating a terminate (TERM)process by the originating transceiver 14 a to the master transceiver 12in response to an ALOHA message from the master transceiver 12. Intransmitting the TERM message, the originating transceiver may alsoidentify the originating device 14 a and the target device 14 b.Responsive to this TERM message, the master transceiver 12 carries outthe operation of checking the states of the originating transceiver 14 aand the target transceiver 14 b, and transmitting to transceiver 14 b aService Termination (STERM) command.

The master transceiver verifies the state of the originating device andthe target device to confirm that both devices are currently engaged forcommunication. If both devices are engaged, the master transceiver 12transmits a reply BACK message to the originating transceiver toacknowledge its termination request and to indicate that the status oforiginating device has been changed to “online” in the master table.Additionally, master transceiver transmits a STERM message to targettransceiver 14 b to indicate that originating transceiver 14 a isterminating data communication with target transceiver 14 b.

Responsive to the STERM message, the target transceiver 14 b carries outthe operation of checking its internal state, terminating the receptionof data, and replying with an acknowledgement (ACK). The targettransceiver 14 b first checks its internal state to ensure that it isengaged in communication with originating transceiver 14 a. If targettransceiver 14 b is engaged with a different transceiver, it replieswith a NACK message to the master transceiver 12 to indicate targettransceiver 14 b is not currently engaged with originating transceiver14 a. If target transceiver 14 b is engaged with transceiver 14 a, thentarget transceiver 14 b stops receiving data from transceiver 14 a andsets its internal state to “online”. Target transceiver 14 b thentransmits to master transceiver 12 an ACK message to indicate that ithas terminated communication with transceiver 14 a and that it haschanged it state to “online”.

When the master transceiver 12 receives the ACK message from the targettransceiver 14 b, it changes the state of target transceiver 14 b in themaster table to “online” and replies to target transceiver 14 b with aconfirmation of the state change. The master transceiver 12 alsoconsiders the data slot which was assigned to originating transceiver 14a as released from use and available for reallocation. When a NACKmessage is received by master transceiver 12 from target transceiver 14b, a severe error is recognized by master transceiver 12 because thisstate was not previously registered with the master table. The mastertransceiver then attempts a STERM sequence with the remaining relatedslave devices until the proper target transceiver is discovered orotherwise ascertained.

When a user of a slave device terminates or interrupts power to theslave or otherwise makes the slave unavailable for communication, thedevice preferably initiates a shutdown sequence prior to suchtermination. The shutdown sequence comprises a shutdown (SHUT) messagefrom the slave device 14 n to the master transceiver 12, in response toan ALOHA broadcast from the master 12. Responsive to the SHUT message,the master 12 replies to the slave device 14 n with a BACK messageindicating that state of slave device 14 n has been changed to “offline”in the master table. Responsive to the BACK message, the slave device 14n changes its internal state to “offline” and shuts down.

Referring now to FIG. 5, a functional block diagram of the Medium AccessControl hardware interface of the present invention is shown andgenerally designated as MAC 66. In general, the MAC 66 is provided atthe Data Link Layer between the Network Layer and the Physical Layer ofthe OSI reference model. More particularly, the MAC 66 provides thehardware circuitry within Medium Access Control (MAC) sublayer of theData Link Layer according the OSI reference model. The Medium AccessControl protocol provided by the present invention provides the softwarefor controlling the processes of the various components of the MAC 66 asdescribed below.

The MAC 66 comprises an integrated circuit or like hardware deviceproviding the functions described herein. The MAC 66 provides meansassociated with each transceiver for connecting multiple data linksreceived from the Logical Link Layer to a single physical TDMA link. TheMAC 66 comprises a communication interface 68 for providingcommunication with the Medium Access Control Protocol 69, a PhysicalLayer interface 70 for communication with the Physical layer, aplurality of slot allocation units (SAU) 72 a through 72 n eachoperatively coupled to the communication interface 68, aMultiplexer/Demultiplexer (Mux/Demux) unit 74 operatively coupled to thePhysical Layer interface 70 and each of the SAU 72 a through 72 n, and aLogical Link Control (LLC) interface 73 connected to each of the SAU 72a through 72 n. A plurality of data interfaces 76 a through 76 n arealso provided for transmitting data to and receiving data from the LLCinterface 73. Each data interface 76 a through 76 n is connected to acorresponding SAU 72 a through 72 n.

Data streams in the present invention will flow in both directions. Forexample, output data will be transmitted from higher level protocolsthrough the DLL hardware 66 and out to the Physical Layer via interface70. Input data is received from the Physical Layer through interface 70into the MAC 66 and then communicated to the higher level protocols.Within the MAC 66 the data path comprises the data interfaces 76 athrough 76 n connected to the SAU 72 a through 2 n, the SAU 72 a through72 n connected to the Mux/Demux 74, and the Mux/Demux 74 connected tothe Physical Layer interface 70. The direction of data flow within eachSAU 72 a through 72 n is controlled by the Medium Access Controlprotocol 69 via communication interface 68. The communication interface68 is preferably separated from the data path through MAC 66. Thisarrangement provides simple data sources, such as audio streamingdevices, a direct connection to the MAC 66.

The Mux/Demux 74 carries out the operation of merging outgoing datastreams from the SAU 72 a through 72 n into a single signal transmittedby the Physical Layer. In the preferred embodiment, a TDMA scheme isused for data transmission. Under the TDMA multiple access definitionscheme, only one device may be transmitting at any given time. In thiscase, the Mux/Demux 74 is connected to the outputs of each SAU. Theoutput of the Mux/Demux 74 is then operatively coupled to the PhysicalLayer interface 70. The Mux/Demux 74 also carries out the operation ofdistributing incoming network data received from the Physical Layer viainterface 70 into the SAU 72 a through 72 n. Generally, the currentlyactive SAU will receive this incoming data.

Referring now to FIG. 6 as well as FIG. 5, a block diagram of an SAUunit is shown and designated as 72. Each SAU unit 72 a through 72 n arestructured and configured as SAU 72. SAU 72 comprises an output bufferunit 78, an input buffer unit 80, a control logic unit 82 connected tothe output buffer unit 78 and the input buffer unit 80, and controlstatus registers 84 connected to the control logic unit 82. The outputbuffer unit 78 stores data to be transmitted from a first device toanother device in a First-In-First-Out (FIFO) buffer (not shown),encodes the buffer's output using a 4B/5B or similar encoding scheme andprovides the resulting bit stream to the Mux/Demux unit 74 via line 86a. The data to be transmitted is provided through the interface 73 vialine 85 a. The input buffer unit 80 receives data from the Physicallayer through the Mux/Demux unit 74 via line 86 b, decodes it accordingthe same 4B/5B or similar encoding scheme, and stores the data in a FIFObuffer (not shown) which is connected to the data path interface 73 vialine 85 b. Lines 85 a and 85 b are operatively coupled to datainterfaces 76 a through 76 n for communication with interface 73. Lines86 a and 86 b are operatively coupled for communication with Mux/Demuxunit 74.

The control logic unit 82 comprises a state machine that controls theoperation of the output buffer unit 78 and input buffer unit 80 as wellas the communication between the MAC and the Logical Link Layer (LLC),and the MAC and the Physical Layer. The values of the control registers84 are set by the LLC above the MAC layer via line 88 and control theoperation of the SAU.

The control registers 84 comprise a SAU enable register 90, a datatransfer direction register 92, a slot start time register 94, and aslot length register 96. The SAU enable register 90 determines whetherthe SAU 72 should transmit or receive data. The data transfer directionregister 92 determines whether the SAU 72 is set up to transmit to thePhysical Layer or to receive from the Physical Layer. The slot starttime register 94 provides the SAU 72 with the time offset of the slotmeasured from the start of the frame, during which the SAU 72 transmitsdata to the Physical Layer.

The slot length register 96 determines the length of the slot. Thestatus registers 84 provide the LLC with information about the currentstate of the SAU. The status registers comprise an input buffer unitempty flag, an input buffer unit full flag, an output buffer unit emptyflag, an output buffer unit full flag, and an input decoder errorcounter. The buffer unit empty flag indicate whether the respectivebuffer units are empty (i.e., contain no data). The buffer unit fullflag indicate whether the respective buffer units are full (i.e., cannotstore additional data). The input decoder error counter indicates thenumber of error detected during the decoding of data arriving from thePhysical Layer.

The SAU 72 transmits or receives data autonomously after being set up bythe LLC. The setup consists of writing appropriate values into the datatransfer direction register 92, the slot start time register 94, and theslot length register 96 and then enabling the SAU 72 by asserting theSAU enable register 90. The slot start time and slot length valuesprovided in registers 94, 96 respectively are designated to thecommunicating device by the network master 12. These values aredetermined by the master 12 in such a way that no two transmitters inthe network transmit at the same time, a requirement of the TDMAcommunication scheme. During transmission, the SAU 72 will monitor thecurrent time offset within the frame and compare it with the slot starttime. When the two values are equal, the SAU 72 will provide thePhysical Layer with encoded data bits from the output buffer 78 untilthe frame has reached the end of the time slot allocated to the SAU 72as determined by the slot length register 96. If the output FIFO bufferis empty during the allocated time slot, the SAU 72 will transmitspecial bit codes indicating to the receiver that there is no data beingtransmitted.

Likewise, the SAU 72 will monitor the current time offset within theframe during data reception and compare it to the slot start timeregister 94. When the two values are equal, the SAU 72 will acquire datafrom the Physical Layer through the Mux/Demux Unit 74, decode it andstore the decoded data in the input FIFO buffer. If the decoder detectsa transmission error, such as a bit code sequence not found in the 4B/5Bencoding table, the data stored in the input FIFO buffer is marked asinvalid and the input decoder error counter is incremented. If thedecoder detects special bit codes indicating empty data, the latter areignored and will not be stored in the input FIFO buffer.

Accordingly, it will be seen that this invention provides a wirelesscommunication network system for isochronous data transfer between nodedevices of the network, which provides a master node device having meansfor managing the data transmission between the other node devices of thenetwork system, which further provides means for framing datatransmission and means for synchronizing the network communicationprotocol, thus providing a means for sharing the transport mediumbetween the node devices of the network so that each node device has adesignated transmit time slot for communicating data. Although thedescription above contains many specificities, these should not beconstrued as limiting the scope of the invention but as merely providingan illustration of the presently preferred embodiment of the invention.Thus the scope of this invention should be determined by the appendedclaims and their legal equivalents.

1. A wireless communication network system comprising at least threetransceivers, each said transceiver having a transmitter and a receiver,one of said transceivers being structured and configured as a masterdevice, said master device structured and configured to manage datatransmission between said transceivers; and a frame definition having amaster slot, a command slot, and a plurality of data slots, said masterslot having a master sync code, said protocol operating in slotted alohamode and time division multiple access mode, said master device managingsaid protocol and said data slots in said protocol.
 2. A wirelesscommunication network system comprising at least three transceivers,each said transceiver having a transmitter and a receiver, one of saidtransceivers being structured and configured as a master device, saidmaster device structured and configured to manage data transmissionbetween said transceivers; and a Medium Access Control hardwareinterface comprising a multiplexer/demultiplexer unit and a plurality ofslot allocation units, said multiplexer/demultiplexer unit operativelycoupled to said plurality of slot allocation units.
 3. A wirelesscommunication network system comprising: (a) at least threetransceivers, one of which is structured and configured as a masterdevice to manage data transmission between said transceivers; (b) atransmitter in each said transceiver; (c) a receiver in each saidtransceiver; and (d) a time division multiple access frame structurehaving a master slot, a command slot, and a plurality of data slots. 4.A wireless communication network system comprising: (a) at least threetransceivers, one of which is structured and configured as a masterdevice to manage data transmission between said transceivers; (b) atransmitter in each said transceiver; (c) a receiver in each saidtransceiver; and (d) a Medium Access Control unit comprising a Physicallayer interface, a multiplexer/demultiplexer unit operatively coupled tosaid Physical layer interface, a plurality of slot allocation unitsoperatively coupled to said multiplexer/demultiplexer unit, an interfaceto higher level protocols operatively coupled to said plurality of slotallocation units.
 5. A method for providing wireless networkcommunication comprising the steps of: (a) providing a mastertransceiver; (b) providing a plurality of slave transceivers incommunication with said master transceiver; (c) synchronizing said slavetransceivers with said master transceiver; (d) providing a Medium AccessControl protocol which is executed in said master transceiver and insaid slave transceivers, said protocol including a Time DivisionMultiple Access frame definition having a master slot, a command slot, aplurality of variable length data slots; (e) requesting a data slot fromsaid master transceiver by a source slave transceiver; (f) assigning tosaid source slave transceiver an assigned data slot by said mastertransceiver; and (g) after said assigning step, transferring data insaid assigned data slot, by said source slave transceiver, to a targetslave transceiver, said data transferring carried out withoutintervention from said master transceiver.